JP2019111860A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of suppressing a difference in contact length between a first side and a second side in the tire width direction. SOLUTION: In a pneumatic tire, a rubber surface layer portion is formed of a first rubber portion formed of a first rubber and a second rubber having a rubber hardness higher than that of the first rubber. A rubber portion is provided, the first rubber portion is arranged on the first side in the tire width direction, the second rubber portion is arranged on the second side in the tire width direction, and the first rubber portion and the second rubber portion are provided. The interface with is arranged between a pair of main grooves arranged on the outermost side in the tire width direction, and the average tire outer diameter on the second side in the tire width direction with respect to the tire equatorial plane is the tire rather than the tire equatorial plane. It is larger than the average tire outer diameter on the first side in the width direction. [Selection diagram] Fig. 4

Description

  The present invention relates to a pneumatic tire.

  Conventionally, for example, a pneumatic tire is provided with a rubber surface layer having an outer surface in the tire radial direction, and the first and second sides of the rubber surface layer in the tire width direction are formed of rubber having different rubber hardness. (E.g., Patent Document 1). In such a pneumatic tire, since a difference in the contact length is generated between the first side and the second side in the tire width direction when going straight, for example, the conicity generated when going straight (force acting in the tire width direction) ) Will be larger.

JP 2012-76593 A

  Then, a subject is providing the pneumatic tire which can suppress that the difference of contact-contact length arises between the 1st side of a tire width direction, and a 2nd side at the time of going straight.

  The pneumatic tire is a pneumatic tire including a plurality of main grooves extending in the tire circumferential direction, and includes a rubber surface layer portion having an outer surface in the tire radial direction, and the rubber surface layer portion is formed of a first rubber A first rubber portion and a second rubber portion formed of a second rubber having a rubber hardness greater than the rubber hardness of the first rubber, the first rubber portion being on the first side in the tire width direction The second rubber portion is disposed on the second side in the tire width direction, and the interface between the first rubber portion and the second rubber portion is a pair of main portions disposed on the outermost side in the tire width direction. The average of the tire outer diameter on the second side in the tire width direction than the tire equatorial plane is larger than the average of the tire outer diameter on the first side in the tire width direction than the tire equatorial plane.

  In addition, the pneumatic tire includes a plurality of land portions divided by the plurality of main grooves and the ground contact end, and the whole of the plurality of land portions is disposed on the second side in the tire width direction than the tire equatorial plane. At least two land portions are provided, and in the shoulder land portions disposed on the second side in the tire width direction on the second side, the difference in tire outer diameter between positions equally spaced from the tire equatorial plane in the tire width direction The average of is larger than the average of the tire outer diameter difference between positions equally distant from the tire equatorial plane in the tire width direction of the middle land portion disposed second outward on the second side in the tire width direction , May be used.

  Further, in the pneumatic tire, the second rubber portion may be disposed outside when the vehicle is mounted.

  In addition, the pneumatic tire includes a plurality of land portions defined by the plurality of main grooves and the ground contact end, and the void ratio of the land portion formed of the first rubber portion is formed of the second rubber portion. The configuration may be smaller than the void ratio of the land portion to be cut.

  In addition, the pneumatic tire may include a center land portion including the tire equatorial plane by being divided by the plurality of main grooves, and the interface may be located at the center land portion.

FIG. 1 is a cross-sectional view of an essential part of a tire meridional surface of a pneumatic tire according to an embodiment. FIG. 2 is a development view of a tread surface of the pneumatic tire according to the embodiment. FIG. 3 is an enlarged view of a III region of FIG. FIG. 4 is a schematic cross-sectional view of main parts of a tire meridional surface of the pneumatic tire according to the embodiment. FIG. 5 is an enlarged view of a V region of FIG. 6 is an enlarged view of a VI area of FIG. FIG. 7 is a view showing a contact shape of a pneumatic tire according to a comparative example. FIG. 8 is a view showing a contact shape of the pneumatic tire according to FIGS. 1 to 6. FIG. 9 is a cross-sectional view of main parts of a tire meridional surface of a pneumatic tire according to another embodiment. FIG. 10 is a cross-sectional view of main parts of a tire meridional surface of a pneumatic tire according to another embodiment.

  Hereinafter, one embodiment of a pneumatic tire will be described with reference to FIGS. 1 to 8. In each of the drawings (the same applies to FIG. 9 and the subsequent figures), the dimensional ratio of the drawings and the actual dimensional ratio do not always match, and the dimensional ratio between the respective drawings does not necessarily match.

  In each figure, the first direction D1 is the tire width direction D1 parallel to the tire rotation axis which is the rotation center of the pneumatic tire (hereinafter, also simply referred to as "tire") 1, and the second direction D2 is The tire radial direction D2 is a diameter direction of the tire 1, and the third direction D3 is the tire circumferential direction D3 around the tire rotation axis. In the tire width direction D1, the first side D11 is also referred to as a first width direction side D11, and the second side D12 is also referred to as a second width direction side D12.

  The tire equatorial plane S1 is a plane perpendicular to the tire rotation axis and located at the center of the tire 1 in the tire width direction D1. The tire meridional plane is a plane including the tire rotation axis and the tire equatorial plane It is a plane orthogonal to the plane S1. The tire equator line is a line at which the outer surface of the tire 1 in the tire radial direction D2 (a tread surface 2a described later) intersects with the tire equator surface S1.

  As shown in FIG. 1, the tire 1 according to the present embodiment includes a pair of bead portions 11 having beads, sidewall portions 12 extending from the bead portions 11 to the outside in the tire radial direction D2, and a pair of sidewall portions The tread portion 2 is connected to the outer end portions of the twelve tire radial directions D2, and the outer surface of the tire radial direction D2 is in contact with the road surface. In the present embodiment, the tire 1 is a pneumatic tire 1 having air introduced therein, and is mounted on a rim 20.

  In addition, the tire 1 is provided with a carcass layer 13 bridged between a pair of beads, an inner liner layer 14 which is disposed inside the carcass layer 13 and is excellent in the function of blocking gas permeation in order to maintain air pressure. Is equipped. The carcass layer 13 and the inner liner layer 14 are disposed along the tire inner circumference across the bead portion 11, the sidewall portion 12, and the tread portion 2.

  The tread portion 2 includes a tread rubber 21 having a tread surface 2 a that contacts the road surface, and a belt portion 22 disposed between the tread rubber 21 and the carcass layer 13. The tread portion 2 also includes a belt reinforcing portion 23 disposed between the tread rubber 21 and the belt portion 22 in order to reinforce the belt portion 22.

  The tread surface 2a has a contact surface that actually contacts the road surface, and among the contact surfaces, the outer ends in the tire width direction D1 are referred to as contact ends 2b and 2c. The tread surface 2a has the tire 1 mounted on a regular rim 20 and is filled with a regular internal pressure. The tire 1 is placed vertically on a flat road surface, and the tread surface 2a is in contact with the road surface when a regular load is applied. Point to Further, of the ground ends 2b and 2c, the ground end 2b on the first widthwise side D11 is referred to as a first ground end 2b, and the ground end 2c on the second widthwise side D12 is referred to as a second ground end 2c.

  In the standard system including the standard on which the tire 1 is based, the regular rim 20 is the rim 20 which is defined for each tire 1 in the standard, for example, if it is JATMA, it is a standard rim, if it is TRA, "Design Rim", ETRTO If it is "Measuring Rim".

  The normal internal pressure is the air pressure specified in each tire 1 in the standard system including the standard on which the tire 1 is based, the maximum air pressure in the case of JATMA, the table in the case of TRA, "TIRE LOAD LIMITS AT VARIOUS COLD The maximum value described in “INFLATION PRESSURES” is “INFLATION PRESSURE” in the case of ETRTO, but is 180 kPa when the tire 1 is for a passenger car.

  The normal load is a load defined in each tire 1 in the standard system including the standard on which the tire 1 is based, the maximum load capacity in the case of JATMA, and the maximum in the above table in the case of TRA. If the value is ETRTO, it is "LOAD CAPACITY", but if the tire 1 is for a passenger car, it is 85% of the corresponding load of internal pressure 180 kPa.

  The belt portion 22 includes at least one (two in the present embodiment) belt layers 22a and 22b. Specifically, the belt portion 22 includes a first belt layer 22a and a second belt layer 22b disposed on the outer side in the tire radial direction D2 than the first belt layer 22a. The number of layers of the belt layers 22a and 22b is not particularly limited.

  The belt reinforcing portion 23 includes a cap reinforcing layer 23a disposed so as to cover the belt layers 22a and 22b in the tire width direction D1. Further, the belt reinforcing portion 23 includes edge reinforcing layers 23b and 23b disposed so as to cover the end portions of the belt layers 22a and 22b in the tire width direction D1.

  As shown in FIGS. 1 and 2, the tread rubber 21 includes a plurality of main grooves 3a and 3b extending in the tire circumferential direction D3. The main grooves 3a, 3b extend continuously in the tire circumferential direction D3. In the present embodiment, the main grooves 3a and 3b extend in a straight shape along the tire circumferential direction D3. However, the present invention is not limited to such a configuration. For example, refraction is repeated to extend in a zigzag shape , Or, for example, may be configured to extend in a wave shape by repeating bending.

  The main grooves 3a, 3b are provided with a portion where the grooves are shallow, so-called tread wear indicator (not shown), for example, so that the degree of wear can be known by exposing as the wear. Further, for example, the main grooves 3a and 3b have a groove width of 3% or more of the distance between the ground contact ends 2b and 2c (the dimension in the tire width direction D1). Also, for example, the main grooves 3a and 3b have a groove width of 5 mm or more.

  In the plurality of main grooves 3a, 3b, the pair of main grooves 3a, 3a arranged on the outermost side in the tire width direction D1 is called shoulder main groove 3a, and is arranged between the pair of shoulder main grooves 3a, 3a The main groove 3b to be formed is called a center main groove 3b. In the present embodiment, although the number of the center main grooves 3b is two, it is not limited to such a configuration, and may be one or three or more, for example.

  The tread rubber 21 includes a plurality of land portions 4 to 8 divided by the main grooves 3a, 3b and the ground contact ends 2b, 2c. In the plurality of land portions 4 to 8, the land portions 4 and 5 divided by the shoulder main groove 3a and the ground contact ends 2b and 2c are called shoulder land portions 4 and 5, and the adjacent main grooves 3a and 3b The lands 6 to 8 which are sectioned by the pair of shoulder lands 4 and 5 are referred to as middle lands 6 to 8.

  Of the middle land parts 6-8, land parts 6, 7 divided by the shoulder main groove 3a and the center main groove 3b are called median land parts 6, 7, and are divided by the center main grooves 3b, 3b. The land section 8 is called the center land section 8. The shoulder land portion 4 on the first widthwise side D11 is referred to as a first shoulder land portion 4, and the shoulder land portion 5 on the second widthwise side D12 is referred to as a second shoulder land portion 5 in the first widthwise direction. The median land portion 6 of the side D11 is referred to as a first median land portion 6, and the median land portion 7 of the second widthwise side D12 is referred to as a second median land portion 7.

  In the present embodiment, the center main grooves 3b, 3b are arranged to sandwich the tire equatorial plane S1. Thus, the center land portion 8 is disposed so as to include the tire equatorial plane S1. Thus, the entire first shoulder land portion 4 and the first median land portion 6 are disposed on the first widthwise side D11 with respect to the tire equatorial plane S1, and the second shoulder land portion 5 and the second median land portion 5 are disposed. The entire portion 7 is disposed on the second widthwise side D12 relative to the tire equatorial plane S1.

  Moreover, land parts 4-8 are provided with a plurality of land grooves 3c and 3d. The plurality of land grooves 3c, 3d extend so as to intersect with the tire circumferential direction D3. Of the land grooves 3c and 3d extending to intersect the tire circumferential direction D3, the land groove 3c having a groove width of 1.6 mm or more is called a width groove 3c, and the groove width is less than 1.6 mm. One land ditch 3d is called sipes 3d. Land portions 4 to 8 may have land grooves whose groove width is smaller than the groove width of main grooves 3a and 3b and extend continuously or intermittently along tire circumferential direction D3. The grooves are called circumferential grooves.

  The tire 1 has a structure that is asymmetric with respect to the tire equatorial plane S1. In the present embodiment, the tire 1 is a tire whose mounting direction to a vehicle is specified, and when mounted on the rim 20, it is a tire whose left or right of the tire 1 is specified to face the vehicle. The tread pattern formed on the tread surface 2 a of the tread portion 2 has a shape that is asymmetric with respect to the tire equatorial plane S1.

  The direction of attachment to the vehicle is displayed on the sidewall 12. Specifically, the sidewall portion 12 is provided with sidewall rubber 12a disposed on the outer side in the tire width direction D1 of the carcass layer 13 so as to constitute the outer surface of the tire, and the surface of the sidewall rubber 12a is displayed Have a department.

  For example, when the vehicle is mounted, one sidewall portion 12 disposed on the inner side (the left side in each drawing, hereinafter also referred to as "the inner side of the vehicle") is an indication to be the inner side of the vehicle (for example, "INSIDE" ) Is attached. Also, for example, when the vehicle is mounted, the other sidewall portion 12 disposed on the outer side (right side in each drawing, hereinafter also referred to as “vehicle outer side”) is an indication that it is the vehicle outer side (for example, “OUTSIDE Etc.) is attached. In the present embodiment, the first widthwise side D11 is an inner side of the vehicle, and the second widthwise side D12 is an outer side of the vehicle.

  As shown in FIG. 3, the tread rubber 21 has a rubber surface layer portion 9 having a tread surface 2 a which is an outer surface in the tire radial direction D 2 and a rubber inner layer disposed on the inner side of the rubber surface portion 9 in the tire radial direction D 2. And a unit 21a. The rubber inner layer portion 21a may be configured not only as a single layer but also as two or more layers. Further, in the rubber inner layer 21a, the rubber inner layer 21a disposed at the innermost in the tire radial direction D2 is referred to as a base rubber, and the rubber surface layer 9 and the other rubber inner layer 21a are referred to as a cap rubber.

  The rubber surface layer portion 9 includes a first rubber portion 9a formed of a first rubber, and a second rubber portion 9b formed of a second rubber having a rubber hardness greater than that of the first rubber. . The rubber hardness is a hardness measured at 23 ° C. based on “JIS K6253-1-2012 3.2 durometer hardness”.

  Although the rubber hardness of each rubber is not particularly limited, for example, the rubber hardness of the first rubber may be 66 to 70, and the rubber hardness of the second rubber may be 70 to 74, for example. Also, for example, the rubber hardness difference between the first rubber and the second rubber is not particularly limited, but may be 2 to 6, for example.

  The rubber surface layer portion 9 includes an interface 9 c between the first rubber portion 9 a and the second rubber portion 9 b. The interface 9c is disposed between the pair of shoulder main grooves 3a and 3a. As a result, distortion occurs at the interface 9c disposed between the pair of shoulder main grooves 3a, 3a at the time of braking, so the distortion becomes a resistance to the road surface. Therefore, since the braking distance can be reduced, the braking performance can be improved.

  Further, in the present embodiment, the interface 9 c is located not on the main grooves 3 a and 3 b but on the land portion 8 so as to appear on the tread surface 2 a. Thereby, distortion generated at the interface 9c becomes a direct resistance to the road surface.

  Moreover, in the present embodiment, the interface 9c is located on the center land portion 8, specifically, on the tire equatorial plane S1. Thereby, the interface 9c is closest to the tire equatorial plane S1 (specifically, includes the tire equatorial plane S1) while the interface land 9c is closest to the tire equatorial plane S1 as the contact pressure at the time of braking increases. It will be located at 8. As a result, the distortion generated at the interface 9c is an effective resistance to the road surface, so that the braking distance can be effectively reduced.

  The interface 9c may be, for example, positioned in the main grooves 3a and 3b and may not appear in the tread surface 2a. The interface 9 c may be located at the middle land portions 6 and 7 although it is located at the middle land portions 6 to 8.

  The interface 9 c may be located at the center land portion 8 but may be located away from the tire equatorial plane S 1. For example, the distance between the interface 9c and the tire equatorial plane S1 is preferably 10% or less, and preferably 5% or less of the distance between the ground contact ends 2b and 2c (the dimension in the tire width direction D1). Is more preferable, and 3% or less is very preferable.

  Moreover, in the present embodiment, the first rubber portion 9a is disposed on the first widthwise side D11, and the second rubber portion 9b is disposed on the second widthwise side D12. That is, the first rubber portion 9a is disposed inside the vehicle, and the second rubber portion 9b is disposed outside the vehicle. As a result, the second rubber portion 9 b having a relatively large rubber hardness is disposed on the vehicle outer side where the ground contact area increases when turning. Therefore, since the rigidity on the outside of the vehicle can be increased, steering stability performance at the time of turning can be improved.

  Returning to FIG. 2, in the present embodiment, the void ratio of the land portions 4, 6, 8 formed of the first rubber portion 9a is the void ratio of the land portions 5, 7, 8 formed of the second rubber portion 9b. It is smaller than the ratio. Thus, the void ratio of land portions 4, 6, 8 formed of first rubber portion 9a having a relatively small rubber hardness is the land portion 5 formed of second rubber portion 9b having a relatively large rubber hardness. , 7 and 8 are smaller than the void ratio. Therefore, it can be suppressed that the difference in rigidity between the land portions 4, 6, 8 of the first widthwise side D11 and the land portions 5, 7, 8 of the second widthwise side D12 becomes large.

  Land portions 4, 6, and 8 formed of the first rubber portion 9a are the first width direction of the shoulder land portion 4 and the median land portion 6 on the first width direction D11, and the center land portion 8. It is an area of the side D11. Therefore, the void ratio of the land portions 4, 6 and 8 constituted by the first rubber portion 9a is equal to the area of the land portions 4, 8 and 8 between the first ground end 2b and the interface 9c (main groove 3a, It is the ratio of the sum of the areas of land grooves 3c and 3d to the sum of land grooves 3c and 3d) not including 3b.

  Further, land portions 5, 7 and 8 formed of the second rubber portion 9b are the second width direction of the shoulder land portion 5 and the median land portion 7 of the second width direction D12 and the center land portion 8. It is an area of the side D12. Therefore, the void ratio of the land portions 5, 7 and 8 formed of the second rubber portion 9b is the area of the land portions 5, 7 and 8 between the second ground end 2c and the interface 9c (main groove 3a, It is the ratio of the sum of the areas of land grooves 3c and 3d to the sum of land grooves 3c and 3d) not including 3b.

  The pitch of the width grooves 3c (the interval in the tire circumferential direction D3) in the median land portion 6 on the first width direction D11 is the pitch of the width grooves 3c in the median land portion 7 on the second width direction D12. It's getting bigger than that. The pitch of the width grooves 3c (except for the sipe 3d) in the shoulder land portion 4 on the first width direction D11 is larger than the pitch of the width grooves 3c in the shoulder land portion 5 on the second width direction D12. It has become.

  Here, the configuration of the land portions 4 to 8 will be described with reference to FIGS. 4 to 6.

  As shown in FIGS. 4 to 6, on the outer surface of the tread portion 2 in the tire radial direction D2, there is a profile surface S2 to be a reference surface. Profile surface S2 is symmetrical on the basis of tire equatorial plane S1. In FIGS. 4 to 6 (the same applies to FIG. 9 and thereafter), the profile surface S2 is illustrated by a broken line.

  The tread surface 2a on the first widthwise side D11 with respect to the tire equatorial plane S1 coincides with the profile surface S2. On the other hand, a part of the tread surface 2a on the second width direction side D12 with respect to the tire equatorial plane S1 is located outside in the tire radial direction D2 than the profile surface S2.

  That is, the land portions 5 and 7 on the second width direction side D12 with respect to the tire equatorial plane S1 are provided with the projecting portions 51 and 71 that project outward from the profile surface S2 in the tire radial direction D2. In addition, in FIGS. 4 to 6 (same as in FIG. 9 and FIG. 10), the protruding portions 51 and 71 are illustrated exaggeratingly.

  In the present embodiment, land portions 5 and 7 disposed on the second width direction side D12 with respect to the tire equatorial plane S1 as a whole, that is, the second shoulder land portion 5 and the second median land portion 7 project The units 51 and 71 are provided. Accordingly, the average of the tire outer diameter R2 on the second width direction D12 than the tire equatorial plane S1 is larger than the average of the tire outer diameter R1 on the first width direction D11 than the tire equatorial plane S1. .

  The amount W1 of the protrusions 51 and 71 protruding from the profile surface S2 to the outside in the tire radial direction D2 (hereinafter, also simply referred to as "protrusion amount") W1 is the same distance W2 from the tire equatorial plane S1 in the tire width direction D1. It can be calculated from the difference between the tire outer diameters R1 and R2 between the distant positions (hereinafter simply referred to as "the tire outer diameter difference") ΔR (= R2-R1). Specifically, the protrusion amount W1 of the protrusions 51 and 71 is 50% of the tire outer diameter difference ΔR.

  As shown in FIG. 5, the second medium land portion 7 is equally divided into three regions A71 to A73 in the tire width direction D1. And each area A71-73 is called inside area A71, center area A72, and outside area A73, respectively from the inside of tire width direction D1.

  The position of the tread surface 2a at which the amount of protrusion of the protrusion 71 of the second medium land portion 7 is maximum, that is, the apex 72 of the protrusion 71 is disposed in the central region A72 of the second median land portion 7. ing. In the present embodiment, the position of the tread surface 2 a at which the tire outer diameter difference ΔR is the largest in the second medium land portion 7 is the apex 72 of the protrusion 71.

  As shown in FIG. 6, the second shoulder land portion 5 is equally divided into three regions A51 to A53 in the tire width direction D1. And each field A51-53 is called inside field A51, center field A52, and outside field A53, respectively from the inner side of tire width direction D1.

  The position of the tread surface 2a at which the protrusion amount of the protrusion 51 of the second shoulder land portion 5 is maximum, that is, the apex 52 of the protrusion 51 is disposed in the central region A52 of the second shoulder land portion 5. . In the present embodiment, in the second shoulder land portion 5, the position of the tread surface 2 a at which the tire outer diameter difference ΔR is maximized is the apex 52 of the protrusion 51.

  By the way, while the central areas A52 and A72 of the land portions 5 and 7 are difficult to contact with the road surface, the apexes 52 and 72 of the protrusions 51 and 71 are disposed on the central areas A52 and A72 of the land portions 5 and 7 It is done. As a result, the land portions 5 and 7 can contact the entire area in the tire width direction D1.

  Further, as shown in FIGS. 5 and 6, the average of the tire outer diameter difference ΔR of the second shoulder land portion 5 is larger than the average of the tire outer diameter difference ΔR of the second median land portion 7 . The maximum value of the tire outer diameter difference ΔR of the second shoulder land portion 5 is larger than the maximum value of the tire outer diameter difference ΔR of the second media land portion 7.

  That is, the maximum value of the protrusion amount W1 of the protrusion 51 of the second shoulder land portion 5 is larger than the maximum value of the protrusion amount W1 of the protrusion 71 of the second medium land portion 7. The maximum value of the protrusion amount W1 of the protrusions 51 and 71 is not particularly limited, but can be, for example, 1% to 3% of the depth of the shoulder main groove 3a.

  The configuration of the pneumatic tire 1 according to the present embodiment is as described above, and next, the operation of the pneumatic tire 1 according to the present embodiment will be described.

  For example, FIG. 7 shows a contact shape of a tire according to a comparative example (land grooves 3c and 3d are not shown in FIG. 7 (the same applies to FIG. 8)). In the tire according to the comparative example, the tread surface 2a is symmetrical with respect to the tire equatorial plane S1 as compared to the tire 1 according to the present embodiment, that is, the tire extends over the entire region in the tire width direction D1. It is a tire changed to the composition that there is no outside diameter difference deltaR.

  And in the tire concerning a comparative example, since the 1st rubber part 9a whose rubber hardness is relatively small on the 1st width direction side D11 is arranged, the grounding length on the 1st width direction D11 (grounding shape The length in the tire circumferential direction D3 is longer than the contact length on the second widthwise side D12. Thereby, since the difference between the ground contact length on the first width direction D11 and the ground contact length on the second width direction D12 is large, for example, the conicity (force acting toward the first width direction D11) generated when going straight is growing.

  On the other hand, in the tire 1 according to the present embodiment, the average of the tire outer diameter R2 on the second widthwise side D12 than on the tire equatorial plane S1 is outside the tire on the first widthwise side D11 than on the tire equatorial plane S1. It is larger than the average of the diameter R1. Thus, in consideration of only the tire outer diameters R1 and R2, the contact length on the second widthwise side D12 is longer than the contact length on the first widthwise side D11.

  Therefore, as shown in FIG. 8, it is possible to suppress the occurrence of the difference between the ground contact length on the first widthwise side D11 and the ground contact length on the second widthwise side D12. Therefore, it is possible to suppress an increase in the conicity generated when traveling straight.

  By the way, the difference in the contact length between the pair of shoulder land portions 4 and 5 tends to be large, while the average of the tire outer diameter difference ΔR of the second shoulder land portion 5 is the tire of the second medium land portion 7 It is larger than the average of the outer diameter difference ΔR. Thereby, it can be effectively suppressed that the difference in the contact length between the pair of shoulder land portions 4 and 5 becomes large.

  From the above, the pneumatic tire 1 according to the present embodiment is the pneumatic tire 1 including the plurality of main grooves 3a and 3b extending in the tire circumferential direction D3, and the rubber surface layer portion 9 having the outer surface in the tire radial direction D2. And the rubber surface layer portion 9 includes a first rubber portion 9a formed of a first rubber, and a second rubber portion 9b formed of a second rubber having a rubber hardness greater than that of the first rubber. The first rubber portion 9a is disposed on the first side D11 in the tire width direction D1, and the second rubber portion 9b is disposed on the second side D12 in the tire width direction D1, and the first rubber portion 9a is disposed. The interface 9c between the portion 9a and the second rubber portion 9b is disposed between the pair of main grooves 3a and 3a disposed at the outermost side in the tire width direction D1, and the first surface of the second rubber portion 9b The average tire outer diameter R2 of the two-side D12 is the tire equator Than the average outer diameter of the tire R1 of the first side D11 in the tire width direction D1 than S1, large.

  According to such a configuration, distortion occurs at the interface 9c between the first rubber portion 9a and the second rubber portion 9b at the time of braking. And since the interface 9c is disposed between the pair of main grooves 3a, 3a disposed on the outermost side in the tire width direction D1, the distortion becomes a resistance to the road surface. Therefore, since the braking distance can be reduced, the braking performance can be improved.

  The first rubber portion 9a having a relatively low rubber hardness is disposed on the first side D11 in the tire width direction D1, whereas the second side D12 in the tire width direction D1 is more than the tire equatorial plane S1. The average of the tire outer diameter R2 is larger than the average of the tire outer diameter R1 of the first side D11 in the tire width direction D1 than the tire equatorial plane S1. Accordingly, it is possible to suppress the difference in the contact length between the first side D11 and the second side D12 in the tire width direction D1 when going straight.

  Further, the pneumatic tire 1 according to the present embodiment includes a plurality of land portions 4 to 8 divided by the plurality of main grooves 3a, 3b and the ground end 2b, 2c, and the plurality of land portions 4 to 8 Among them, at least two land portions 5 and 7 disposed on the second side D12 in the tire width direction D1 than the tire equatorial plane S1 are provided at least two, and disposed at the outermost side on the second side D12 in the tire width direction D1. The average of the tire outer diameter difference ΔR between the positions of the shoulder land portion 5 separated by the same distance from the tire equatorial plane S1 in the tire width direction D1 is the second outside on the second side D12 in the tire width direction D1. The middle land portion 7 is configured to be larger than the average of the tire outer diameter difference ΔR between positions equally separated from the tire equatorial plane S1 in the tire width direction D1.

  According to such a configuration, the shoulder land portion 5 disposed at the outermost side on the second side D12 in the tire width direction D1 against the fact that the difference in the contact length between the pair of shoulder land portions 4 and 5 tends to be large. The average of the tire outer diameter difference ΔR between positions equally spaced from the tire equatorial plane S1 in the tire width direction D1 is the middle land portion 7 disposed second outward on the second side D12 in the tire width direction D1. It is larger than the average of the tire outer diameter difference ΔR. Thereby, it can suppress that the difference of the contact length between a pair of shoulder land parts 4 and 5 becomes large.

  Moreover, in the pneumatic tire 1 according to the present embodiment, the second rubber portion 9 b is configured to be disposed outside when the vehicle is mounted.

  According to such a configuration, the second rubber portion 9b having a relatively large rubber hardness is arranged outside when the vehicle is mounted, while the ground contact area of the region outside when the vehicle is mounted becomes large when turning. . As a result, the rigidity of the outer region can be increased when the vehicle is mounted, so that the steering stability during turning can be improved.

  Further, the pneumatic tire 1 according to the present embodiment includes a plurality of land portions 4 to 8 divided by the plurality of main grooves 3a, 3b and the ground contact end 2b, 2c, and is configured by the first rubber portion 9a. The void ratio of the land portions 4, 6, 8 to be formed is smaller than the void ratio of the land portions 5, 7, 8 formed of the second rubber portion 9b.

  According to such a configuration, the void ratio of the land portions 4, 6 and 8 constituted by the first rubber portion 9a having a relatively small rubber hardness is constituted by the second rubber portion 9b having a relatively large rubber hardness. It is smaller than the void ratio of land areas 5, 7 and 8. As a result, it is possible to suppress an increase in the difference in rigidity between land portions 4, 6, 8 of the first side D11 in the tire width direction D1 and land portions 5, 7, 8 of the second side D12.

  Further, the pneumatic tire 1 according to the present embodiment includes the center land portion 8 including the tire equatorial plane S1 by being partitioned by the plurality of main grooves 3a and 3b, and the interface 9c is the center land. It is the structure of being located in the part 8.

  According to such a configuration, since the interface 9c is located at the center land portion 8, distortion generated at the interface 9c is a direct resistance to the road surface. Moreover, since the interface 9c is located at the center land portion 8 closest to the tire equatorial plane S1 against the contact pressure at the time of braking becomes larger as the tire equatorial plane S1 is closer to the tire equatorial plane S1, distortion generated at the interface 9c However, it is an effective resistance against the road surface.

  In addition, the pneumatic tire 1 is not limited to the structure of embodiment mentioned above, Moreover, it is not limited to the effect mentioned above. Of course, the pneumatic tire 1 can be variously modified without departing from the scope of the present invention. For example, as a matter of course, one or a plurality of configurations, methods, and the like according to various modifications described below may be arbitrarily selected and adopted as the configuration, the method, and the like according to the above-described embodiment.

(1) In the pneumatic tire 1 according to the above-described embodiment, the apexes 52 and 72 of the protrusions 51 and 71 are disposed in the central areas A52 and A72 of the land portions 5 and 7, respectively. However, the pneumatic tire 1 is not limited to such a configuration. For example, the apexes 52 and 72 of the protrusions 51 and 71 may be arranged in the inner regions A51 and A71 of the land portions 5 and 7, respectively.

  Also, for example, as shown in FIG. 9, the apex 52 of the protrusion 51 may be disposed in the outer area A53 of the land portion 5. According to such a configuration, it is possible to effectively suppress the difference in the contact length from becoming larger as the difference in the contact length tends to become larger as the tire width direction D1 gets more outward.

(2) Further, in the pneumatic tire 1 according to the above-described embodiment, the protruding portions 51 and 71 have the apexes 52 and 72. However, the pneumatic tire 1 is not limited to such a configuration. For example, as shown in FIG. 10, the amount by which the protrusion 51 protrudes from the profile surface S2 is the same over the entire area of the land portion 5 in the tire width direction D1, ie, the protrusion 51 includes the apex 52. It may be configured not to

(3) Moreover, in the pneumatic tire 1 according to the above embodiment, the protruding portions 51 and 71 are provided only in the land portions 5 and 7 disposed on the second width direction side D12 with respect to the tire equatorial plane S1. The structure is However, the pneumatic tire 1 is not limited to such a configuration. For example, the protruding portions may be provided also on land portions 4, 6, 8 disposed on the first width direction side D11 relative to the tire equatorial plane S1.

(4) Further, in the pneumatic tire 1 according to the embodiment, the average of the tire outer diameter difference ΔR of the second shoulder land portion 5 is the tire of the middle land portion 7 adjacent to the second shoulder land portion 5 This configuration is larger than the average of the outer diameter difference ΔR. However, the pneumatic tire 1 is not limited to such a configuration although such a configuration is preferable. For example, the average of the tire outer diameter difference ΔR of the second shoulder land portion 5 may be the same as the average of the tire outer diameter difference ΔR of the middle land portion 7, or, for example, the middle land portion The configuration may be smaller than the average of the tire outer diameter difference ΔR of No. 7.

(5) Further, in the pneumatic tire 1 according to the above-described embodiment, the maximum value of the tire outer diameter difference ΔR of the second shoulder land portion 5 corresponds to that of the middle land portion 7 adjacent to the second shoulder land portion 5. This configuration is larger than the maximum value of the tire outer diameter difference ΔR. However, the pneumatic tire 1 is not limited to such a configuration although such a configuration is preferable. For example, the maximum value of the tire outer diameter difference ΔR of the second shoulder land portion 5 may be the same as the maximum value of the tire outer diameter difference ΔR of the middle land portion 7, or, for example, The configuration may be smaller than the maximum value of the tire outer diameter difference ΔR of the land portion 7.

(6) Further, in the pneumatic tire 1 according to the above-described embodiment, the second rubber portion 9b is disposed outside when the vehicle is mounted. However, the pneumatic tire 1 is not limited to such a configuration although such a configuration is preferable. For example, the second rubber portion 9b may be arranged inside when the vehicle is mounted.

(7) Further, in the pneumatic tire 1 according to the above-described embodiment, the void ratio of the land portions 4, 6, 8 formed of the first rubber portion 9a is the land portion 5 formed of the second rubber portion 9b. , 7 and 8 are smaller than the void ratio. However, the pneumatic tire 1 is not limited to such a configuration although such a configuration is preferable.

  For example, the void ratio of land portions 4, 6, 8 formed of the first rubber portion 9a is the same as the void ratio of land portions 5, 7, 8 formed of the second rubber portion 9b. Also, for example, the void ratio of the land portions 4, 6, 8 formed of the first rubber portion 9a is larger than the void ratio of the land portions 5, 7, 8 formed of the second rubber portion 9b. , May be used.

(8) Further, the pneumatic tire 1 according to the above-described embodiment is configured to be a tire whose mounting direction to a vehicle is designated. However, the pneumatic tire 1 is not limited to such a configuration. For example, the pneumatic tire 1 may be configured to be a tire whose mounting direction to a vehicle is not designated. In such a configuration, the tread pattern has a shape that is point symmetrical with respect to an arbitrary point on the tire equator, or a shape that is symmetrical with respect to the tire equator.

DESCRIPTION OF SYMBOLS 1 ... Pneumatic tire, 2 ... Tread part, 2a ... Tread surface, 2b ... 1st grounding end, 2c ... 2nd grounding end, 3a ... Shoulder main groove, 3b ... Center main groove, 3c ... land groove (width groove) , 3d ... land groove (sipe), 4 ... 1st shoulder land section, 5 ... 2nd shoulder land section, 6 ... middle land section (1st media land section), 7 ... middle land section (2nd media land land Part 8) Middle land part (center land part) 9 Rubber surface layer part 9a first rubber part 9b second rubber part 9c interface 11 bead part 12 sidewall part 12a ... sidewall rubber, 13 ... carcass layer, 14 ... inner liner layer, 20 ... rim, 21 ... tread rubber, 21 a ... rubber inner layer portion, 22 ... belt portion, 22 a ... first belt layer, 22 b ... second belt layer, 23 ... belt reinforcing portion, 23 a ... cap reinforcing layer, 3b: edge reinforcing layer, 51: projection, 52: apex, 71: projection, 72: apex, A51: inner area, A52: central area, A53: outer area, A71: inner area, A72: central area, A73 ... outside region, D1 ... tire width direction, D2 ... tire radial direction, D3 ... tire circumferential direction, D11 ... first width direction side (first side), D12 ... second width direction side (second side), R1 ... Tire outer diameter, R2: Tire outer diameter, ΔR: Tire outer diameter difference, S1: Tire equatorial plane, S2: Profile surface

Claims (5)

A pneumatic tire comprising a plurality of main grooves extending in the tire circumferential direction, the pneumatic tire comprising:
A rubber surface portion having an outer surface in the tire radial direction;
The rubber surface layer portion includes a first rubber portion formed of a first rubber, and a second rubber portion formed of a second rubber having a rubber hardness greater than that of the first rubber,
The first rubber portion is disposed on the first side in the tire width direction,
The second rubber portion is disposed on the second side in the tire width direction,
The interface between the first rubber portion and the second rubber portion is disposed between a pair of main grooves disposed at the outermost side in the tire width direction,
The pneumatic tire wherein the average of the tire outer diameter on the second side in the tire width direction than the tire equatorial plane is larger than the average of the tire outer diameter on the first side in the tire width direction than the tire equatorial plane. A plurality of land portions defined by the plurality of main grooves and the ground end;
Among the plurality of land portions, at least two land portions, the whole of which is disposed on the second side in the tire width direction with respect to the tire equatorial plane, are provided,
The average of the tire outer diameter difference of the positions apart from the tire equatorial plane by the same distance in the tire width direction of the shoulder land portion disposed outermost on the second side in the tire width direction is the second side in the tire width direction The pneumatic tire according to claim 1, which is larger than the average of the tire outer diameter difference between positions equally distant from the tire equatorial plane in the tire width direction in the middle land portion disposed second outward.   The pneumatic tire according to claim 1, wherein the second rubber portion is disposed outside when the vehicle is mounted. A plurality of land portions defined by the plurality of main grooves and the ground end;
The air-filled according to any one of claims 1 to 3, wherein the void ratio of the land portion formed of the first rubber portion is smaller than the void ratio of the land portion formed of the second rubber portion. tire. A center land portion including the tire equatorial plane is provided by being divided by the plurality of main grooves,
The pneumatic tire according to any one of claims 1 to 4, wherein the interface is located at the center land portion.

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